Drilling method and apparatus



2 Sheets-Sheet 1 J. W. BORMAN EVAL DRILLING METHOD AND APPARATUSOriginal Filed Juno 24, 1965 Oct. 27, 1970 Oct. 27, 1970 J, w, BORMANEIAL Re. 26,975

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26,975 DRILLING METHOD AND APPARATUS Jess W. Borman, Cincinnati, Ohio,and `lohn P. Schaefer, Bennington, Ind., by The Wheelabrator Corp.,assignee, Mishawaka, Ind., a corporation of Delaware Original No.3,342,086, dated Sept. 19, 1967, Ser. No. 466,778, June 24, 1965.Application for reissue Apr. 18, 1969, Ser. No. 824,009

Int. Cl. B35b 35/00, 51/06 U.S. Cl. 77-5 13 Claims Matter enclosed inheavy brackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT F THE DISCLOSURE A method and apparatus for supplying coolantto a tool for machining a hole in a workpiece by pulsating the flow ofcoolant through the tool so as to effect improved cutting eiciency andtool life.

This invention relates to a metal drilling method and apparatus and,more particularly, to a method and apparatus for cooling a drill and`workpiece during a drilling operation.

One aspect of this invention is predicated upon the discovery thatdrilling eiiiciency and tool life of an oil hole drill or a drill inwhich cutting fluid is fed through the drill interior to the workpieceis substantially improved if the coolant pressure is regularly varied orpulsed during the drilling operation. It has therefore been an objectiveof this invention to increase tool life and cutting eiciency of a drillby improving both the method and apparatus for supplying coolant to thecutting edge of the drill.

Another objective of this invention has been to improve the cuttingefficiency and tool life of conventional oil hole drills or drills inwhich coolant is supplied to the drill tip through the interior of thedrill. We have found that regularly varying the pressure or pulsing thecoolant or cutting fluid supplied to the drill produ-ces much longertool life than supplying the coolant at a high but constant pressure.Heretofore the general theory was to supply as much fluid as possible orto flood the drill tip in order to increase the efficiency. We havefound, however, that better results are achieved, and the tool lifeincreased by approximately fifty percent, by regularly, as for examplefifty times a minute, interrupting or decreasing the coolant pressuresupplied to the drill so that a pulsing ow is supplied to the drill tip.

We have also found that tool speed and feed rates may be substantiallyincreased if the coolant to an oil hole drill is pulsed or supplied atregularly varying pressures.

The explanation for this increased efficiency and tool life isapparently very complex and involves both metal cutting and heattreating principles. One feasible explanation which is at leastpartially empirically provable, is that the interrupted coolant flowallows the chips to heat up so that when suddenly cooled, they fractureinto smaller chips than would otherwise occur and are easily flushedthrough the tintes of the drill.

Another objective of this invention has been to provide an inexpensive,portable unit useable with any machine tool which is capable of drillinga hole to enable that machine to be used to drill holes with a drill ofthe type in which coolant or cutting fluid is supplied to the drill tipor cutting edge through the interior of the drill.

An oil hole drill requires coolant to be supplied to the tool under muchhigher pressures than those available from conventional machine toolcoolant pumps. There- 'United States Patent O JCC fore an inexpensiveportable pump unit for use with an oil hole drill mounted in aconventional machine ttcd with a low pressure coolant pump is a highlydesirable unit which substantially broadensvthe cutting capabilitiesspectrum of a conventional machine tool.

Another objective of this invention has been to provide a portable highpressure coolant unit including a pneumatic motor driven hydraulic pumpfor supplying coolant to an oil hole drill. The primary advantage of apneumatic motor driven unit is that it is inexpensive to operate andless subject to break down under adverse operating conditions than moreconventional electric motor driven units. The inexpensive operationderives primarily from the fact that most machine shops have airpressure available and unused in the form of a ninety p.s.i. pressureline running throughout the shop for purposes of driving small pneumaticmotors of portable hand tools or for blowing chips and dust away toclean machines and workpieces. By utilizing this untapped capacity, theunit is much less expensive to operate than electrically driven units.

Another objective of this invention has been to provide an improvedportable coolant supply unit for converting a conventional low pressurecoolant supply machine tool into one capable of use with oil holedrills. To increase the portability of such a unit, the pump issupported upon a roller mounted hollow base which serves the dualfunction of acting as a hose reel when the unit is in storage or intransit between machines.

These and other objects and advantages of the invention of thisapplication will be more readily apparent from the following descriptionof the drawings in which:

FIGURE l is a perspective view of the coolant pump unit of thisinvention applied to a drill press,

FIGURE 2 is a perspective view, partially in diagrammatic form, of thepumping unit of this invention applied to a turret lathe,

FIGURE 3 is a cross-sectional view of the pump and motor unit of FIGUREl,

FIGURE 4 is a diagrammatic illustration of a second embodiment of theinventive coolant pumping unit of this application, and4 FIGURE 5 is agraph of tool life plotted against feed rate to illustrate thedifferential in tool life achieved from different coolant deliverymethods.

Referring first to FIGURE l, and the preferred embodiment of theinvention, a coolant pumping unit 10 is shown as applied to aconventional drill press 1l. The drill press 11 includes theconventional vertical slideway 12 for supporting the vetrically moveabletool head (not shown) having a rotatable spindle 14 for supporting adrill bit 15. The drill press 11 also includes a work support table 13upon which is mounted a jig 16 having a guide bushing 17 for supportingthe drill against lateral deflection as it is moved into a workpiece 18clamped in the jig 16. The drill press 11 and jig 16 form no part ofthis invention and are only illustrated to show the operativeenvironment of use of the invention of this application.

The coolant pumping unitll) is a portable unit rwhich may easily beremoved from one machine and attached to another whenever an oil holedrilling operation is programmed for a machine. It consists of acylindrical, hollow, sheet metal base 20 having a lower flange 21mounted upon a plurality of rollers or casters 22. Hose retainerbrackets 23 are welded or otherwise secured to the flange 21 so as toextend vertically parallel but spaced from the peripheral wall of thebase 20. These brackets 23 permit the pump hoses and electrical lines tobe wound upon the base 20- in the fashion of a hose reel with the lowerportion of the base 20 serving as a reel and the brackets 23 serving ashose retainers.

In the preferred embodiment, the pump 27 and the motor 26 for drivingthe pump, are a unitary assembly 25 mounted on the top of the hollowbase 20. The pump assembly 25 could, however, be mounted within thehollow base if so desired.

The motor 26 is of the pneumatic type in which air under pressure issupplied to the motor 26 via an air supply line 28, through a regulator32 and solenoid controlled valve 33, to a pump inlet line 34. A by-passline 35 including a ow control or needle valve 36 is provided around thesolenoid 33 between the regulator 32 and the pump inlet line 34 so as topass a limited volume of air to the pump motor when the solenoid 33 isin the valve closed position. When the needle valve 36 is partially openand the solenoid is in the closed position, air through the by-pass 35is operative to drive the motor 26 at a slow rate so as to pump a smallvolume of cutting fluid or coolant to the drill 15 at a low pressure.This low pressure cutting oil or coolant is useful to start a drillingoperation before the drill enters the workpiece so as to limit thesplashing. After the drill enters the workpiece, the solenoid may beenergized and high pressure coolant supplied without excessivesplashing. Alternatively, the needle valve 36 may be closed completely,in which event, only high pressure coolant will be supplied to the drilland that only when the solenoid 33 is energized.

Solenoid valve 33 is a conventional electrically actuated valve to whichpower is supplied from a conventional 110 volt A.C. source via ilne 37through a foot pedal 38 control switch. As an alternative, the switchmay be controlled automatically by tool feed displacement. Additionally,rather than being electrically controled, the vave may be pneumaticalycontrolled from an air operated microswitch.

The source of this air under pressure is one of the common lines of theplant or factory Where the coolant unit is to be used. Most factorieshave such aitsupply lines running throughout the plant for cleaningparts or machines so that this is a convenient source of motive power.

Coolant is supplied to the pump assembly from the machine coolantreservoir (not shown) via conduit 29. Since nearly all machines areequipped with coolant reservoirs, there is no need for the coolant unit10 to be equipped with its own coolant source. Pulsating coolant orcoolant in which the pressure of the coolant regularly varies at apredetermined frequency, is supplied from the pump to drill 15 viaconduit 30 and rotary union or arbor 31. The rotary union or arbor 31 isa conventional coupling having a non-rotating collar 24 within which adrill supporting rotatable shaft is mounted and through which coolant issupplied to the drill 15.

While the coolant pumping unit 10 is usually used in connection with adrill press, it is equally adaptable to use in a turret lathe asillustrated in FIGURE 2. Lathes are often used to support a non-rotatingdrill 40 fed axially relative to a rotating workpiece 41. When drillingdeep holes, it is preferable to use an oil hole drill in which coolantis supplied through the interior of the drill via a passage 42 to thecutting tip 43.

An oil holed rill may only be used in a turret lathe if provision ismade for supplying coolant at high pressure to the drill. In theembodiment of FIGURE 2, this provision consists of a coolant supply tube44 mounted in the turret 46 so as to interconnect the drill oil holepassage 42 with a central aperture 45 of the turret 46. The tube 44 isbent so that its free end extends vertically and is co-axial with theaxis of rotation of the indexable turret 46. Connecting the upper end ofthe tube 44 to the output of the coolant pump unit l0 is a snap-fitrotary union 47 and the flexible supply conduit 30.

Referring now to FIGURE 3 and the preferred embodiment of the pump unit10, as stated above the unit comprises the reciprocal pneumatic motor 26for operating the reciprocating iluid pump 27. Reciprocating of thepneumatic motor 26 is controlled by a valve assembly 48. This pump,motor, and valve assembly, per se, form no part of the invention of thisapplication and therefore will only be described in general terms.

Considering first the motor 26, it will be seen that it includes a motorcylinder body 53 in the form of a ported casting within which a piston54 is receiprocable. The piston 54 has an enlarged flange or head 55 atits lower end which is in sliding engagement with the inner wall 56 ofthe cylinder body 53. Guiding the upper end of the piston 54 is aretainer ring 57 secured in a seat 58 defined between the upper edge ofthe cylinder body 53 and the lower edge of a piston guide cap or head59. The inner wall 60 of this head 59 is confgurated so as to provide apartially cylindrical bore for guiding support of the motor piston 54 aswell as a recess 61 for recepition of a portion of the motor valvereciprocating mechanism. Attached to the upper end of the piston 54 bymeans of bolts 64 is a laterally extending arm having a recess 66 at itsouter end for reception of a tripper rod 67 of the valve aS- sembly 48.i

The lower end or bottom of the piston 54 is defined by a generallysemi-spherical recess 69 and flat bottom surface 70 of the piston head55. The semi-spherical surface 69, the bottom surface 70, together withthe cylinder side wall 56 and bottom surface 71 of the cylinder detinethe lower motor chamber 72. The upper chamber 73 of the motor 26 isdefined between the bottom of retainer 57, the top of piston head 55,the cylindrical upper section 74 of piston 54 and the cylindrical wall56 of the cylinder. The effective area against which the pressuresupplied to the upper chamber 73 acts to force the piston 54 downwardlyas viewed in FIGURE 3 is the upper surface 75 of the piston head 55.This surface is much smaller in area than the total area of the lowerpiston surfaces 69, 70 so that when equal pressure are applied to bothsides, the total force applied to the bottom of the piston is muchgreater than that applied to the top with the result that the piston ismoved upwardly.

Depending from the bottom of motor piston 54 is a piston rod 76. Thisrod is attached to piston 54 by means of a nut 77 threaded on to theupper end 78 of the rod. The nut 78 is in turn clamped by means of aclamp nut 79 within a recess 80 in the bottom of the piston 54. Thepiston rod 76 extends through an aperture 81 of the motor cylinder body53 and supports the pump piston as is explained hereinafter.

The porting through the motor cylinder body 53 to the upper chamber 73or the air motor consists of a pressure port connected via a verticalconduit 86 to an inlet port 87 of the upper chamber 74. The lowercharnber 72 is connected via a conduit 88 to the reciprocating valveassembly 48. This valve assembly 48 is in turn connected to the pressureconduit 86 via a conduit 89. In operation, the pressure port 85 isconnected to an air pressure line of approximately fty to ninety p.s.i.depending upon the size drill and other variables such as splash, holedepth, etc.

The valve assembly 48 is controlled by the tripper rod 67. This rod 67is reciprocable within a pair of aligned apertures 115, 116 of the motorcylinder body 53. Reciprocation of the rod is controlled by the arm 65attached to the top of the motor piston 54. For this purpose, it isprovided with an enlarged head 117 connected to the body 118 of the rodby a thin stem 119. At the upper end of its stroke, the arm 65 engagesthe bottom of the head 117 causing the tripper rod 67 to be movedupwardly. At the lower end of its stroke and in the position illustratedin FIGURE 3, the arm 65 engages a shoulder 120 of the rod 67 and forcesthe rod downwardly from the position illustrated in this gure. By thesemovements, the rod 67 controls a toggle 121 which in turn controls aspool valve of the reciprocating valve assembly 42.

The toggle 121 is the connecting link between the pneumatic motor 26 andvalve 48. It is pivotally mounted upon a pivot pin 122 which is in turnsupported by the valve casing 123. One end of the toggle 121 isengageable with a pair of spaced shoulders 126, 127 of the tripper rod47. Upon downward movement of the rod 67, shoulder 126 engages the topof the toggle 121 and pushes it downwardly while on upward movement ofthe rod, the shoulder 127 engages the bottom of the toggle 121 andpushes it upwardly.

The valve 48 consists of a two piece body or casing 123 secured to themotor body 53 and within which a two piece spool 134 is movable. To keepdust and dirt out of the valve, a cap 129 is secured over it.

The end 130 of the toggle opposite end 125 is engageable in one positionwith a head 131 attached to stem 132 of spool 134. In the other positionto which the toggle is movable, it engages a shoulder 133 of the spool134 to force the spool 134 downwardly from the position illustrated inFIGURE 3.

Spool 134 is slidable within a bore 136 of the valve housing 123. Thishousing is ported so as to cooperate with the ports 88, 89 of the airmotor cylinder body 53 to control the connection of the motor lowerchamber 72 with either exhaust or high pressure.

As shown in FIGURE 3, the conduit 88 in the cylinder body 53 isconnected to exhaust or atmospheric pressure through valve ports 145.High pressure in conduit 89 is at this time precluded from enteringconduit 88 by a tapered seat of the valve 134 engaging a correspondinglytapered seat 141 of the housing 123.

When the spool 134 is moved upwardly from the position shown in FIGURE 3by the toggle 121, a rubber seat 142 of the spool engages a shoulder 143of the housing 123 and is so doing, blocks the passage of air throughthe conduit 88 to exhaust via passage 145 in the valve housing 123.Simultaneously, the upward displacement of the spool 134 results in theopening of the tapered seat 140, 141 between the spool and the housingso that high pressure air may pass from the inlet port 85, through theconduit 89, past the seat 140, 141 and into the conduit 88 to the lowerchamber 72 of the air motor.

In order to preclude the escape of high pressure air in conduit 89through the lower portions of the bore 136 in the housing 123, a leathergasket 144 is attached to the bottom of the spool 134 by a Washer 146and nut 147 threaded onto the threaded lower end 148 of the spool.

The pump 27 consists of a piston 150 movable within a pump cylinder 151.This cylinder is threaded into and depends from the motor body 53.Vertical movement of a piston 150 within the cylinder 151 is controlledby the piston rod 76 of motor 26. This piston 150 acts as a valve incooperation with a valve plate 152 attached to the bottom of piston rod76 by means of a nut 153 threaded onto the lower end of the piston rod76.

A conventional packing ring 154 is secured between the piston rod 76 andthe sleeve 151 to prevent leakage of fluid from the pump into the motor.The packing ring 154 is secured within a recess 155 in the top of thecylinder 151 by a cap or washer 156. The washer 156 is secured againstthe top of cylinder 151 by a spring 157 compressed between washer 157and a washer 158 seated in a recess 159 of the motor body 53. Any fluidwhich does inadvertently pass the packing ring or gland 156 is exhaustedfrom the motor body 53 through an exhaust conduit 160 which is connectedto atmospheric pressure within a pump casing 161.

Attached to the lower end of the pump cylinder 151 is a one-way ballvalve 165. This valve consists of a valve body 166 having a restrictedpassage 167 which supports a ball 162.

Normally the ball 168 rests upon the restricted passage defining section171 of the valve body 166 so as to close the restricted passage 167.Thus, fluid entrapped within the lower chamber 172 of the pump cannotflow out through the restricted passage 167. However, if the pressureabove the ball 168 is less than the pressure beneath 6 the ball 168, theball 168 will be lifted from its seat so that fluid may ow into thechamber 172. This occurs when the piston 150 is moved upwardly upon anupward stroke of the motor piston 54.

The pump piston 150 is slidably mounted upon the motor piston rod 76.Its sliding movement is however limited or restricted by valve plate 152a ndby a compression spring 175 mounted over the rod 76 between a rodflange 174 and the upper side of the piston 150. This spring normallybiases the piston 150 downwardly into engagement with the valve plate152.

To permit the flow of fluid through the piston 150, the plate 152 has aplurality of apertures 176 through which fluid may pass from the lowerpump chamber 172 into the upper chamber 173.

Upon a downstroke of the motor piston 54 and piston rod 76, fluidtrapped in the lower chamber 172 of the pump by the one-way check valve165, acts upon the exposed lower surface 178 of the piston 150 to forcethe piston 150 upwardly relative to the valve plate 152 and thus createsa passage for uid entrapped in the lower chamber 172 to move into theupper chamber 173 through the apertures 176 in the piston 150. On theupstroke, the piston 150 remains seated against the valve plate 152 sothat tluid is forced out of the pump via an exit tube 180 whichcommunicates with the upper pump chamber 173. In the preferredembodiment, the pressure of the fluid exiting through the tube 180 isfour times as great as the pressure of the air entering through port 85to drive the pump motor. However, a seven to one ratio pump, in whichthe fluid pressure is seven times as great as the entering air pressure,has also been found satisfactory for this use.

In operation, air pressure is supplied to the pump unit by connecting aline 34 to the inlet port 85. This air pressure is usually in theneighborhood of 50 to 90 pounds per square inch. The lower end of thepump cylinder 151 is connected to a source of coolant by the hose 29 andhose clamp 182. The end of the hose 29 opposite the end attached to pump27 is fitted iwith a 30 mesh (per lineal inch) screen filter (not shown)which rest swithin the coolant pump or tank (not shown) of the machinewith which the unit is being used. The outlet tube 180 of the pump 27 isconnected via the conduit 30 to the rotary union or arbor 32 or 47.

With the pump unit in the position illustrated in FIG- URE 3, highpressure air is supplied from the port 85 through conduits 86 and 87 tothe upper chamber 73 of the motor. Simultaneously, the lower chamber 72of the motor is connected via conduit 88 and valve ports 145 of thevalve assembly to exhaust or atmospheric pressure. In this position ofthe valve, the motor piston 54 continues to move downwardly until thearm 65 engages the shoulder 120 of the tripper rod 67, causing the rodto move downwardly from the position illustrated in FIGURE 3 and topivot the toggle 121 about the pivot pin 122. This results in upwardmovement of the spool 134 until the rubber gasket 142 of the spool seatsand seals against the shoulder 143 of the valve housing 123 so that thelower motor chamber 72 is no longer connected to atmospheric pressure.This spool movement results in the lower chamber 72 being connected tothe high pressure port 85 via the conduits 86, 89 and 88 so that thesame high pressure exists in the lower chamber 72 as in the upperchamber 73. However, because the piston area in the lower chamber 72 ismuch greater than the piston area in the upper chamber 73, the piston 54is caused to move upwardly until the arm 65 engages the head 117 of thetripper rod 67 and moves the rod into its upper position. This resultsin the shoulder 127 engaging the lower side of the toggle 121, causingthe toggle to pivot in a clockwise direction as viewed in FIGURE 3 untilthe bottom of the toggle engages the shoulder 133 of the spool 134 andforces the spool downwardly back into the position shown in FIGURE 3.

As the motor piston 54 and pistron rod 76 move upwardly, valve plate 152and piston 150 move up forcing any fluid entrapped in the upper chamber173 out through the outlet pipe 180 of the pump. Simultaneously, itdraws a vacuum on the lower chamber 172 between the ball 168 and thevalve plate 152, causing the ball 168 to lift so that Huid is pulledinto the lower chamber 172 from the coolant sump. When thereafter, themotor piston 54 moves downwardly, that fluid trapped in the lowerchamber 172 between valve plate 152 and ball 168 lnust move from thelower chamber 172 into the upper chamber 173` It does so by forcing thepiston 150 upwardly relative to the valve plate 152 by compressingspring 175 so that fluid passes between valve plate 152 and piston 150through ports 176 into the upper chamber 173 as the piston rod 76 movesdownwardly. Thereafter, on the upstroke, that iluid which has justpassed into the upper chamber 173 upon the downstroke of the pistonA rod76, is forced out of the upper chamber 173 and exits through the outlettube 180. The pressure at which this fluid exits through the outlet tube180 in the preferred embodiment is approximately four times as great asthe air pressure entering through the inlet port 85. It is, of course, apulsating pressure which varies from maximum pressure to zero duringeach pump cycle because of the reciprocal nature of the pump and becausethere is no accumulator to even out the pressure.

As an alternative pumping unit for supplying pulsating coolant to atool, a second embodiment is illustrated in FIGURE 4. In thisembodiment, a constant pressure pump 200 such as a rotary vane pump isused to supply coolant from a sump or tank 201 to a rotary union 202 andsubsequently to a tool. The rotary union may be the same union 47illustrated in FIGURE 2 or the union 32 illustrated in FIGURE 1.

The pump 200 is driven by a conventional electric motor 204. Insertedinto the pump outlet line 205 between the pump 200 and the rotary union202 is a conventional solenoid valve 206 which, when the solenoid 210 isenergized, blocks the flow of fluid to the rotary union 202 and tool. Inorder to handle the back pressure in line 205 when the valve 206 isclosed, a conventional fluid pressure accumulator 207 is inserted inline 205 between the pump 200 and valve 206.

In this embodiment, the solenoid 210 of solenoid valve 206 is controlledby a switch 211. When the switch 211 is closed, the solenoid 210 isenergized and the valve 206 blocks the ow of uid to the union 202 andthus to the tool (not shown); but when ie-energized, the valve 206routes the uid from conduit 205 to the rotary union and subsequently tothe tool.

Controlling the energization of switch 211 is a rotary cam 215 mountedon the output shaft of a gear reduction unit 217. The gear reductionunit is driven from an electric motor 218 at any selected speed within alimited range. The preferred speed of the cam plate 215 was found to beabout l2 or 13 revolutions per minute so that the four lobes 219 of thecam closed the switch 211 at a rate of approximately 50 times perminute. This resulted in a pulsating pump pressure being supplied to therotary union 202 and thus to the oil hole drill (not shown) underpressure which pulsed at a rate of approximately 50 pulses per minute.With this arrangement the pressure varied or pulsed betweenapproximately 70 p.s.i. and 120 p.s.i. While the systems disclosed inFIGURES l and 2 are considered to be preferable to that illustrated inFIGURE 4, this latter system was satisfactory and did establish that apulsating pressure of even this frequency and of this pressuredifferential was satisfactory to prolong the life of the tool and toincrease the maximum tool feed rate.

Test results utilizing the setup of FIGURE l (indicated as Pulsatingline on graph) and FIGURE 4 (indicated on graph as Constant Pressurew/Induced Pulsation) as well as a conventional constant pressure pump(Constant Pressure") for supplying the tool with coolant under pressureare shown graphically in FIGURE 5. To obtain these results, half-inchdiameter holes were drilled in 4340 steel of 300 to 325 Brinnelhardness. In each case the drill was a half-inch diameter, high-speedsteel, oil hole tapered web drill with a point angle of 118 degrees anda clearance of 17 degrees. The drill was fed into the workpiece at afeed rate of .005 inch per revolution and the cutting iiux was a solubleoil. Tool life end points were established whenever a wearland of .015inch was observed on the lip of the drill. The results of these testswere as follows:

Toor. LIFE (No. of holes drilled] FIGURE 1034m- ()onstant stantPressure` In- FIGURE 1 Cutting pressure (3.0 duced pulsation Pulsating(2.0 speci gal/min. 200 (2.5 gah/min.) gai/min.) ft.j'inii1ute p.s.i.)(70 to 120 p.s.i.) (0 to 200 p.s.i,)

35 is 3a 36,24 is 24, 26 5a, 43, 34 34, 40, 49

Graphically, the results are shown in FIGURE 5. These tests clearlyestablish that pulsating the coolant supplied to an oil hole drillresults in a tool life approximately `60 percent greater than thatachieved using a constant pressure coolant source. And this was trueeven though the quantity of coolant supplied to the drill with theconstant pressure source was as much as 50 percent greater than thequantity of coolant supplied with a pulsating source.

It was also found during the test of the oil hole drill pulsatingcoolant supply versus constant pressure coolant source, that thepulsating coolant was much more eflicient than the constant pressure. Infact, the pulsating enabled the drill penetration maximum rate (drillfeed multiplied by drill speed) to be increased substantially over thatpossible with constant pressure coolant.

This invention not only contributes to the tool life and feed rate ofoil hole drills but also provides a convenient portable accessory unitwhich may be used with conventional jig borers or drill presses or evenlathes to adapt these machines for use with oil hole drills even thoughthey have no coolant source or a coolant source of insufficient pressureto enable the machine to be used for this purpose.

While only two embodiments of the invention have been disclosed anddescribed herein, those skilled in the art to which this inventionpertains will readily appreciate numerous changes and modificationswhich may be made in the invention without departing from the spiritthereof. Therefore we do not intend to be limited except b" the scope ofthe appended claims.

Having described our invention we claim:

[1. The method of drilling a hole in a workpiece which comprises:

effecting relative rotational movement between a workpiece and a drillwhile said drill remains in engagement with said workpiece,

supplying coolant uid through a passagway in said drill terminatingadjacent to the tip thereof, said coolant uid being supplied to saidworkpiece so as to cool said drill and workpiece and ush chips away fromthe tip of said drill, and

varying the pressure of the coolant tiowirig through said drill by atleast 30 percent at a frequency of at least 30 times per minute so as toregularly pulse the iluid ow to said drill tip.]

2. The method of drilling a hole in a workpiece which comprises:

effecting relative rotational movement between a workpiece and a drillwhile said drill remains in engagement with said workpiece,

supplying coolant liquid to said drill tip through a passagewayterminating adjacent said tip at a low pressure at the time said drillinitially contacts and partially enters said workpiece,

thereafter supplying coolant [fluid] liquid through said passageway insaid drill to said workpiece at a high pressure so as to cool said drilland workpiece and lush chips away from the tip of said drill, and

regularly varying the pressure of the coolant liquid llowing throughsaid drill so as to pulse the uid flow to said drill tip.

3. The method of drilling a hole in a workpiece which comprises:

effecting relative rotational movement between a workpiece and a drillwhile said drill remains in engagement with said workpiece,

supplying coolant liquid to said drill tip through a passagewayterminating adjacent said tip at a low pressure at the time said drillinitially contacts and partially enters said workpiece,

thereafter supplying coolant [fluid] liquid through said passageway insaid drill to said workpiece at a high pressure so as to cool said drilland workpiece and ush chips away from the tip of said drill andregularly varying the pressure of the coolant liquid owing through saiddrill by at least percent so as to pulse the uid tlow to said drill tip.

4. In a machine tool having a rotatable tool mounted in a rotatablemember, said rotatable tool including an axial passageway terminatingadjacent to the tip of said tool, the improvement which comprises aportable unit for supplying coolant through said axial passageway ofsaid tool, said portable unit comprising:

a floor supported base,

a single acting reciprocal fluid pump mounted upon said base, said pumpbeing operable to regularly vary the pressure of iluid being pumpedthrough an outlet of said pump,

inlet conduit means having one end attached to the inlet of said pumpand the other end adapted to be inserted into the coolant reservoir ofthe machine tool with which the unit is to be utilized,

outlet conduit means connected at one end to the outlet of said pump,

a rotary union attached to the other of said outlet conduit and adaptedto be attached to said rotatable member of said machine tool,

pneumatic motor means mounted upon said base and operatively associatedwith said pump so as to control tluid liow from said pump to said rotaryunion, and

control means operable to control said pneumatic motor means.

5. In a machine tool apparatus having a rotatable tool mounted in arotatable member of the machine tool, said rotatable tool including anaxial passageway terminating adjacent to the tip of said tool, theimprovement which comprises a portable unit for supplying coolantthrough said axial passageway to the tool, said portable unitcomprising:

a lightweight, hollow, oor supported base,

a reciprocal lluid pump mounted upon said base, said pump being operableto regularly vary the pressure of liuid being pumped through an outletof said pump so as to generate a pulsating flow,

inlet conduit means having one end attached to the inlet of said pumpand the other end adapted to be inserted into the coolant reservoir ofthe machine tool with which the unit is to be utilized,

outlet conduit means connected at one end to the outlet of said pump,

a rotary union attached to the other end of said outlet conduit andadapted to be attached to said rotatable member of said machine tool,

pneumatic motor means supported upon said base and operable to drivesaid pump,

valve means supported upon said base and operatively associated withsaid motor means so as to control said motor and thus control tluid owfrom said pump to said rotary union, and

switching means operable to control valve means.

6. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent to the tipthereof, the improvement which comprises a coolant supply unit forsupplying coolant through said passageway of said drill, said colantsuppuly unit including:

abase,

a single piston, reciprocating pump supported by said base,

a first conduit for supplying coolant from a reservoir to said pump,

a second conduit for supplying coolant from said pump to said drill, and

means including said pump for supplying coolant through said drillpassageway at regularly varying pressures whereby said coolant pulses inits flow through said drill.

7. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent to the tipthereof, the improvement which comprises a coolant supply unit forsupplying coolant through said passageway of said drill, said coolantsupply unit including:

a base,

a reciprocal piston pump supported by said base,

a first conduit for supplying coolant from a reservoir to said pump,

a second conduit for supplying coolant from said pump to said drill, and

means including said pump for supplying coolant through said drillpassageway at regularly varying pressures whereby said coolant pulses inits flow through said drill,

said means including a pneumatic motor for drving said pump from an airpressure source.

8. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent to the tipthereof, the improvement which comprises a coolant supply unit forsupplying coolant through said passageway of said drill, said coolantsupply unit including:

a base,

a reciprocal piston pump supported by said base,

a first condiut for supplying coolant from a reservoir to said pump,

a second conduit for supplying coolant from said pump to said drill,

means including said pump for supplying coolant through said drillpassageway at regularly varying pressures whereby said coolant pulses inits ow through said drill,

said means including a pneumatic motor for drving said pump,

a source of air pressure connected by an air conduit for operating saidmotor, and

valve means in said air conduit for controlling the operation of saidmotor.

9. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent to the tipthereof, the improvement which comprises a coolant supply unit forsupplying coolant through said passageway of said drill, said coolantsupply unit including:

a base,

a reciprocal piston pump supported by said base,

a first conduit for supplying coolant from a reservoir to said pump,

a second conduit for supplying coolant from said pump to said drill,

means including said pump for supplying coolant through said drillpassageway at regularly varying 1 l pressures whereby said coolantpulses in its ow through said drill, said means including a pneumaticmotor for driving said pump, a source of air pressure connected by anair conduit to said motor for operating said motor, solenoid operatedvalve means in said air conduit for controlling the ilow of air throughsaid air conduit to said motor, and an electrical switch for controllingsaid valve means. 1I). In a drilling apparatus which includes a drill ofthe type having a longitudinal passageway including an outlet openingadjacent to the tip thereof, the improvement which comprises a coolantsupply unit for supplying coolant through said passageway of said drill,said coolant supply unit including:

a base, a reciprocal piston pump supported by said base, a first conduitfor supplying coolant from a reservoir to said pump, a second conduitfor supplying coolant from said pump to said drill, means including saidpump for supplying coolant through said drill passageway at regularlyvarying pressure whereby said coolant pulses in its flow -y through saiddrill,

said means including a pneumatic motor for driving said pump,

a source of air pressure connected by an air conduit to said motor foroperating said motor,

valve means in said air conduit for controlling the flow of air throughsaid air conduit to said motor, control for opening said valve means,and

means including by-pass air conduit means around said valve means foroperating said pneumatic motor at a slow speed until sald valve openswhereby Huid at a relatively low pressure may be supplied to said drilluntil said drill enters said workpiece and thereafter uid at arelatively high pressure may be supplied to said drill.

11. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent to the tipthereof, the improvement which comprises a coolant supply unit forsupplying liquid coolant through said passageway of said drill, saidcoolant supply unit including:

a Pump,

a lirst conduit for supplying liquid coolant from a reservoir to saidpump,

a second conduit for supplying liquid coolant from said pump to saiddrill,

means including said pump for supplying liquid coolant through saiddrill at regularly varying pressures whereby said liquid coolant pulsesin its flow through said passageway of said drill,

said means including a valve in one of said conduits and means foroperating said valve at a regular frequency.

12. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent to the tipthereof, the improvement which comprises a coolant supply unit forsupplying liquid coolant through said passageway of said drill, saidcoolant supply unit including:

a pump,

a motor for operating said pump,

a first conduit for supplying liquid coolant from a reservoir to saidpump,

a second conduit for supplying liquid coolant from said pump to saiddrill,

means including said pump for supplying liquid coolant through saiddrill at regularly varying pressures whereby said liquid coolant pulsesin its ow through said passageway of said drill,

said means including a valve and rotating cam means for operating saidvalve at a regular frequency.

12 13. In a drilling apparatus which includes a drill of the type havinga longitudinal passageway including an outlet opening adjacent to thetip thereof, the improvement which comprises a coolant supply unit forsupplying liquid coolant through said passageway of said drill, saidcoolant supply unit including:

a tluid pump,

an electric motor for operating said pump,

a first conduit for supplying liquid coolant from a reservoir to saidpump,

a second conduit having a pressure accumulator therein for supplyingliquid coolant from said pump to said drill,

a solenoid operated valve in said second conduit for 15 controlling theow of [uid] liquid from said pump to said drill,

electrical switch means for controlling said solenoid valve,

a rotary cam operable to control said switch means,

and

means for driving said cam so as to control the opening and closing ofsaid switch means at a regular frequency whereby said valve operates tovary the pressure of [duid] liquid supplied through said drillpassageway by pulsing said [Huid] liquid tlow.

[14. The method of drilling a hole in a workpiece which comprises:

effecting relative rotational movement between a workpiece and a drillwhile said drill remains in engagement with said workpiece,

supplying coolant uid through a longitudinal passageway in said drillterminating near the tip thereof to said workpiece so as to cool saiddrill and said workpiece and to ush chips away from the cutting tip ofsaid drill, and

regularly varying the pressure of the coolant ilowing through said drillso as to pulse the fluid llow to said drill tip.]

[15. The method of drilling a hole in a workpiece which comprises:

effecting relative rotational movement between a workpiece and a drillwhile said drill remains in engagement with said workpiece,

supplying coolant fluid through a longitudinal passageway in said drillterminating near the tip thereof to said workpiece so as to cool saiddrill and workpiece and flush chips away from the tip of said drill, andvarying the pressure of the coolant flowing through said drill at afrequency of at least 30 times per 5U minute so as to regularly pulsethe fluid flow to said drill tip] [16. The method of drilling a hole ina workpiece which comprises:

effecting relative rotational movement between a workpiece and a drillwhile said drill remains in engagement with said workpiece,

supplying coolant uid through a longitudinal passageway in said drillterminating near the tip thereof to said workpiece so as to cool saiddrill and workpiece and flush chips away from the cutting tip of saiddrill, and

regularly varying the pressure of the coolant owing through said drillby at least 30 percent so as to pulse the fluid ow to said drill tip]17. In a drilling apparatus which includes a drill of the type having alongitudinal passageway including an outlet opening adjacent tothe tipthereof, the improvement which comprises a coolant supply unit forsupplying liquid coolant through said passageway of said drill, saidcoolant supply unit including:

a pump,

a first conduit for supplying liquid coolant from a reservoir to saidpump,

a second conduit for supplying liquid coolant from said pump to saiddrill, and

patent.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original UNITED STATESPATENTS Portereld 77-5 Mirrielees 77-55.3 Thacher 10-106 Maker 29-106 141/1937 Harris et al 103-50 10/1942. Shaner et al 29-106 9/1958 White29--106 4/1961 Wenz 77-55.3

4/1965 Gulbert 51--267 FOREIGN PATENTS 12/ 1957 Great Britain. 9/1959Great Britain.

m FRANCIS s. HUSAR, Primary Examiner U.S. Cl. X.R.

mung oram- O i i UNITED STATES PATENT omer CERTIFICATE OF CRRECTONPatent No. 26,975 (reissue) Barea october 27, 1970 Inventor) Jess R.Berman and John P. Schaefer It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the specification:

Col. 2, line 50: please change the word vetrically to read verticallyCol. 3, line 29: change the word ilne to read line Col. 3, line33:change the word vave to read valve Col. 3, line 33: change the wordpneumaticaly to read --pneum'atically Y Y Coil. 3, line 74: change theword reciproatinq to read Col. 4 line l5: change the word recepition toread reception i I A Col. 4, line 35: change the word pressure to readpressures Col. 4, line 49: change the number 74 to read 73 In theclaims:

Claim 4, Col. 9, line 42: after the word other insert end Claim 5, Col.l0, line 3: after the word bontrol insert Claim 6, Col. l0, line 8: theword Colant should read Claim', Col.l 10, lines 8 and 9: "suppulylIshould read supply Claim '7, Col. l0, line 37: the word drving should bechanged to read driving Claim l0, Col. ll, line 25: change the wordpressure to read u slam L r SEALED' l j 5 i971 :SEAL: y Attest: Edwmnach, In mw I; n m.

@omissione of Patat@

